Method for processing soft vegetable foodstuffs into crumbs

ABSTRACT

Soft and moist vegetables are kneaded, severed and partially homogenized by a feed screw which rotates in a barrel and are admitted into a mincing unit wherein the partially homogenized material is severed by knives of a rotor which is surrounded by an apertured cylindrical stator. The comminuted material is thereupon caused to pass through the holes of an extruder and is severed behind the extruder to yield discrete crumbs which can be used as animal fodder or dried and ground to yield flour or farina, particularly flour or farina which can be used for the baking of tortillas. Vegetables which are admitted into the barrel are freshly harvested (such vegetables may include banana peels) or cooked. For example, dried grains of maize can be cooked in the presence of water and rinsed prior to admission into the barrel.

This is a division of application Ser. No. 600,112, filed July 29, 1975.

BACKGROUND OF THE INVENTION

The present invention relates to a method and apparatus for processingvegetable foodstuffs, and more particularly to improvements in a methodand apparatus for comminuting corn, wheat, banana peels or other typesof vegetable foodstuffs which are to be consumed by humans and/oranimals. Still more particularly, the invention relates to improvementsin a method and apparatus for comminuting soft vegetable foodstuffs.

Many industrially processed foodstuffs of vegetable origin must beconverted into a readily flowable pulverulent or similar state prior tofinal processing. Thus, wheat, rye and other types of grains must betreated in a mill to be converted into flour or farina prior to baking,prior to making of macaroni or analogous foodstuffs, or prior to directsale to consumers. The making of flour for bread and/or other bakeryproducts involves an intensive drying of grains, slight wetting andsubsequent comminution in one or more passes of a flour mill. Also, manyvegetable foodstuffs which are being prepared for consumption by animalsare introduced (in dried condition) into a crushing mill to becomminuted to a desired degree of fineness. The thus comminuted materialis thereupon compacted to form pellets. In each instance, the vegetablesmust be dried prior to comminution, i.e., freshly harvested vegetablesare dried prior to introduction into a mill, even if the actualcomminution must be preceded by a slight or pronounced increase ofmoisture content. Thus, at least the majority of vegetable foodstuffsmust become hard (as a result of drying) before they are ready to becomminuted in a flour mill or the like.

Pronounced drying of certain types of vegetable foodstuffs prior tocomminution and conversion into shapes which are expected by theconsumers presents many problems. Thus, the taste, the behavior duringbaking or cooking, the color and/or certain other characteristics ofmany types of flours are less than satisfactory as a direct or indirectresult of drying prior to conversion into a pulverulent or like state.Moreover, satisfactory drying of many types of vegetable foodstuffsprior to comminution takes up relatively long periods of time or suchdrying must be promoted by resorting to bulky, complex and expensivedrying units which contribute excessively to the cost of the ultimateproduct. Still further, traditional mills which are used for the makingof flour, farina and analogous pulverulent substances are satisfactoryfor comminution of cereal grains or the like but are totally unsuitedfor comminution of many other types of vegetables. For example, a flourmill cannot be used for conversion of freshly harvested vegetables intoflour or farina, especially if the freshly harvested foodstuffs containa high percentage of moisture. Water and other liquids squeezed out ofthe freshly harvested foodstuffs would immediately contaminate a flourmill and would prevent orderly evacuation of comminuted material.

Attempts to convert freshly harvested vegetables with a high moisturecontent into a pulverulent or like state by resorting to conventionalpaste mills or dough mixers have met with little success. In fact, theconversion of raw vegetables into a paste merely aggrevates the problemswhich arise in connection with drying before the paste can be reducedinto a pulverulent or like state. Thus, a paste mill or an analogousmachine can be used solely for the making of vegetable pastes; however,its use in conversion of fresh or raw vegetables into flour or farinamerely contributes to the overall cost and prolongs the conversion ofraw materials into a mass of flour-like consistency.

The drying of grains presents additional problems due to the fact thatsuch foodstuffs comprise several layers, especially outer layers, whichprevent rapid expulsion of moisture from the interior of the grain.Therefore, the drying of grains prior to comminution in a flour mill orthe like invariably involves prolonged drying by air or expensive forceddrying in specially designed ovens. It is not desirable to grind grainsprior to complete or sufficient drying because the preliminary grindingmust be followed by extensive drying prior to renewed grinding for thepurpose of obtaining flour, farina or a substance of similarconsistency. In accordance with certain presently known proposals,freshly harvested or partially dried grains are treated to form a pulpyor dough-like mass, and such mass is mixed with dry flour or farinaprior to further comminution. The admixture of flour or farina to doughis necessary in order to enable a conventional mill to treat suchsubstances for the purpose of making flour or the like. The justdescribed recirculation of substantial quantities of flour or farinathrough a mill (together with a mass of pasty or like consistency)contributes significantly to the bulk and energy requirements of theapparatus.

SUMMARY OF THE INVENTION

An object of the invention is to provide a novel and improved method ofconverting moist freshly harvested (or moistened) vegetable foodstuffsinto a form or shape which is best suited for immediate consumption orfor further processing into a flowable (pulverulent or granular) state.

Another object of the invention is to provide a method of the justoutlined character which can be carried out by relatively simple andcompact apparatus whose energy requirements are low and which can beused for processing of several types of vegetables.

A further object of the invention is to provide a novel and improvedmethod of making flour or farina which can be used for the baking oftortillas or analogous foodstuffs for consumption by humans.

An additional object of the invention is to provide a method ofconverting moist (raw or dried and subsequently wetted) vegetables intoflowable products which can stand long periods of storage and which canbe converted into baked products for humans consumption or animal fodderprior to or after sale to consumers or animal owners.

Still another object of the invention is to provide a novel and improvedmethod of converting raw or moistened vegetables into porous crumbs.

A further object of the invention is to provide a novel and improvedmethod of converting fresh banana peels into animal fodder in the formof crumbs, pellets or the like.

An additional object of the invention is to provide a simple, compact,versatile and inexpensive (especially energy-saving) apparatus for thepractice of the above outlined method.

An ancillary object of the invention is to provide the improvedapparatus with novel means for kneading, fragmentizing and homogenizingfresh or dried and subsequently moistened vegetable foodstuffs.

Another object of the invention is to provide the apparatus with a noveland improved unit which can comminute kneaded material to a desired sizeand shape.

A further object of the invention is to provide the apparatus with noveland improved means for converting kneaded, comminuted and homogenizedvegetable substances into porous pellets and with novel and improvedmeans for converting pellets into flour or farina.

One feature of the invention resides in the provision of a method ofcontinuously processing soft and moist vegetable foodstuffs,particularly vegetables having a relatively high moisture content in therange of 20-60 percent, preferably 33-55 percent. Such vegetables mayinclude grains of corn, wheat, rye, banana peels and/or many others. Themethod comprises the steps of subjecting moist vegetables to apronounced compressing or condensing, kneading and attendant first orpreliminary homogenizing action to form a mass of fragmentizedvegetables (this can be achieved by conveying vegetables along one ormore helical paths which are defined by the threads of a rotating feedscrew and the internal surface of a cylindrical barrel for the feedscrew whereby the width of each path preferably does not exceed 13millimeters and is less than 3 millimeters and the path or paths do notoccupy more than at most 25-30 percent of the interior of the barrel),comminuting the mass including subdividing the mass into a plurality ofsmaller batches (e.g., elongated strands) and severing the batches toform a plurality of fragments, homogenizing the thus severed andfragmentized material, and converting such material into discretecrumbs.

If the vegetables are grains of corn or maize, and if the ultimateproduct is to be a flowable pulverulent or granular substance (e.g.,flour or farina) which can be used for the making of tortillas, themethod preferably further comprises the steps of drying the crumbs andcomminuting the thus dried crumbs to form a flowable pulverulent orgranular product. For the making of such flour or farina, the methodpreferably further comprises the steps of cooking dried grains of cornin the presence of water and chalk, rinsing the thus cooked grainswhereby the rinsed grains constitute the aforementioned moist vegetableswhich are thereupon subject to the compressing, kneading and firsthomogenizing action.

The steps of kneading, comminuting, homogenizing and converting thevegetables and fragments thereof are preferably carried out while thematerial to be treated is sealed or substantially sealed from thesurrounding atmosphere, e.g., in a preferably composite housing whichaccommodates the aforementioned feed screw, the subdividing and severingunit, the homogenizing means (which may form part of the subdividing andsevering unit), and the converting means which may include a plate-likeextruder with holes for the passage of strands of homogenized materialand blades which sever the strands to subdivide each strand into aplurality of porous crumbs. The communiting, homogenizing and convertingsteps preferably immediately follow the kneading, comminuting andhomogenizing steps, respectively. The pressure which is supplied by therotating feed screw is preferably selected in such a way that itsuffices to maintain moist vegetables, the mass, the batches and thehomogenized material in motion in the course of the kneading,comminuting, homogenizing and converting steps.

If the vegetables are cooked in the presence of water prior to kneading,(e.g., when such vegetables are grains of corn or maize), the kneading,comminuting, homogenizing and converting steps are preferably carriedout while the vegetables and portions thereof are still hot and containat least some of the water which is being added in the course of thecooking step.

In many instances, the material which is to be converted into crumbs canbe properly homogenized only if the comminuting step comprisesrepeatedly subdividing the mass into batches (e.g., strands) and eachsubdividing step is followed by a severing step which may be carried outby resorting to one or more sets of orbiting knives. Each severing stepmay be followed by a discrete homogenizing step. The aforementionedknives can cut the batches of fragments into smaller fragments havingmaximum dimensions in the range of 1-2 millimeters. The maximumdimensions of crumbs may be in the range of 5 millimeters.

As mentioned above, the converting step may include passing homogenizedmaterial through the holes of a suitable extruder and severing thestrands as they issue from the holes so that each strand can yield alarge number of porous and moist crumbs.

If the crumbs are to be dried and thereupon ground so as to yield aflowable pulverulent or granular product (i.e., flour or farina), thedrying step may comprise heating the crumbs on an endless conveyor orheating and drying the crumbs in several stages at least one of which(e.g., the first stage) may comprise vibrating, shaking or otherwiseagitating the crumbs to enhance the exchange of moisture between thematerial of the crumbs and the moisture withdrawing medium.

The speed of the material is preferably reduced immediately precedingthe converting or crumb-forming step. This can be achieved as follows:The comminuting step may comprise conveying the mass through at leastone set of apertures in a cylindrical stator and the converting step maycomprise conveying homogenized material through the holes of anextruder. The speed at which the mass is conveyed through the aperturesof the stator (e.g., through the last of two or more sets of apertures)is at least four times the speed at which the material passes throughthe holes of the extruder.

The novel features which are considered as characteristic of theinvention are set forth in particular in the appended claims. Theimproved apparatus itself, however, both as to its construction and itsmode of operation, together with additional features and advantagesthereof, will be best understood upon perusal of the following detaileddescription of certain specific embodiments with reference to theaccompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a diagrammatic partly elevational and partly verticalsectional view of an apparatus which can be used for the making of cornmeal or farina such as is suited for the baking of tortillas;

FIG. 2 is an enlarged vertical sectional view of the kneading,comminuting or mincing and crumb-forming units in the apparatus of FIG.1;

FIG. 3 is an enlarged transverse vertical sectional view of thecomminuting unit, substantially as seen in the direction of arrows fromthe line III of FIG. 2;

FIG. 4 is a perspective view of the main portion of a stationaryapertured cylindrical stator in the comminuting unit of FIG. 2;

FIG. 5 is a longitudinal vertical sectional view of a portion of amodified apparatus which comprises an upright comminuting unit;

FIG. 6 is a longitudinal vertical sectional view of a simplifiedcomminuting unit;

FIG. 7 is a similar longitudinal vertical sectional view of a furthercommuniting unit; and

FIG. 8 is a similar longitudinal vertical sectional view of stillanother comminuting unit.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring first to FIGS. 1, 2, 3 and 4, there is shown an apparatuswhich embodies one form of the invention and can be utilized to convertfreshly harvested or dried vegetables (e.g., corn Co) into crumbs Cr orinto a readily flowable pulervulent or granular substance Fl (which maybe flour or farina). The apparatus comprises an optional preconditioningunit A (here shown as a cooker), a combined kneading, first homogenizingand first comminuting unit B, a second homogenizing and comminuting unitC, a crumb-forming unit D, a main or final conditioning unit E (hereshown as a drier), and a third communiting unit or mill F.

The unit B (hereinafter called kneading unit for short) comprises ahorizontal housing member or barrel 12 for a rotary feed screw 1 whichis driven by a main prime mover 5 (preferably a variable-speed electricmotor). The housing of the motor 5 and a heating and/or cooling jacket14 for the barrel 12 are mounted on a suitable platform or base 8. Theinlet 6 of the barrel 12 is disposed below a hopper or magazine 7 whichcan receive preconditioned material from the cooker A by way of aconduit 306 containing a pump 305. The pump 305 is preferably of thevariable-delivery type. The feed screw 1 has a cylindrical core or shank10 for a single or multiple helix or thread 11. The diameter Di of thecore 10 is preferably only slightly less than the inner diameter of thebarrel 12 so that the thread 11 defines one or more relatively narrowhelical paths 13 wherein the material advances toward and into the unitC (hereinafter called mincing unit for short). Each path 13 isrelatively long to insure a high satisfactory and desirable kneadingwith attendant homogenization as well as pronounced comminution ofconveyed material. For example, the width of the helical path 13 betweenthe internal surface of the barrel 12 and the external surface of thecore 10 (as considered radially of the barrel axis 22) may be in therange of 3-13 millimeters. It is assumed that the diameter Di is orapproximates 250 millimeters. The manner in which the jacket 14 may heator cool the cylinder 12 forms no part of the invention. For example, thejacket 14 may contain one or more coils which extend longitudinallyand/or circumferentially of the barrel 12 and can be connected with asource of heating or cooling fluid. The core 10 of the screw 1 ispreferably hollow to allow for internal heating or cooling with a fluid.For example, that end of the feed screw 1 which is nearest to the outputshaft of the motor 5 may be operatively connected with a suitabledistributor or manifold which admits fresh coolant or fresh heatingfluid into and receives spent coolant or spent heating fluid from theinterior of the core 10.

The mincing unit C is installed in a sleeve-like intermediate housingmember 15 which is secured to a flange at the left-hand end of thebarrel 12 (as viewed in FIG. 1 or 2) by means of screws, bolts oranalogous fasteners 16. The mincing unit C comprises a mobilecomminuting means or rotor 21 which is coaxial with the feed screw 1 andis threadedly connected to the latter by means of a stub 21', stationarycommuniting means here shown as a hollow apertured cylindrical stator 20which surrounds the rotor 21 with minimal clearance, and a stationarytubular guide 17 which constitutes or forms part of homogenizing meansand is installed in the sleeve 15 so as to surround the stator 20. Theforward end of the rotor 21 is received in a friction bearing 31 whichis mounted in the smaller-diameter front end portion 20a of the stator20. The portion 20a is located in front of a collar 20b which has anannulus of relatively large openings 20c and is urged against theadjacent end face of the guide member 17 by a cover 18 forming part of aconnecting device 3 which constitutes a portion of the housing andsupplies comminuted material to the crumb-forming unit D. The connectingdevice 3 comprises a support 9 which defines an arcuate first channel 3afor material issuing from the openings 20c of the stator 20 and adownwardly diverging second channel 3b immediately above a disk-shapedor plate-like extruder 4 of the unit D. The cover 18 is inserted intoand is secured to the support 9 by bolts, screws or analogous fasteners51. The manner in which the right-hand end of the support 9 is affixedto the sleeve 15 and/or base 8 is not specifically shown in the drawing.

The collar 20b of the stator 20 urges the right-hand end face of theguide member 17 against the flange of the barrel 12; thus, the cover 18insures that the components 17 and 20 cannot rotate in the sleeve 15.Any, even minute, angular displacements of the guide member 17 arefurther prevented by one or more radial screws 45 which mesh with thesleeve 15 and whose conical tips extend into notches machined into theperiphery of the guide member 17.

The construction of the rotor 21 in the mincing unit C is shown indetail in FIGS. 2 and 3. This rotor comprises a solid cylindrical body21A whose peripheral surface is formed with two circumferentiallycomplete annular recesses 23, 24 having a trapezoidal cross-sectionaloutline (as viewed in a plane including the common axis 22 of the feedscrew 1 and rotor 21). Each of the recesses 23, 24 is subdivided intoseveral (e.g., twelve) axially parallel cells 23A, 24A, (see FIG. 3) bya set of radially arranged elongated knives 25. Each knife 25 has anenlarged (T-shaped or wedge-like) inner end portion 25a which isslidably guided in the complementary inner end portion of one of severalelongated flutes 26 machined into the periphery of the cylindrical body21A and extending in parallelism with the axis 22. The flutes 26 extendall the way to the front end face of the body 21A so that one or moreknives 25 can be withdrawn from the respective flutes upon detachment ofthe cover 18 from support 9 and upon subsequent withdrawal of the stator20 from the interior of the guide member 17.

If desired, the knives 25 can form integral parts of the cylindricalbody 21A, i.e., this body can be treated in a suitable machine tool tobe formed with discrete cells 23A and 24A. However, discrete knives 25are preferred at this time because they can be removed for inspection,sharpening or replacement while the cylindrical body 21A remains coupledto the feed screw 1. Owing to the aforementioned trapezoidalcross-sectional outline of the recesses 23, and 24, the depth of eachcell 23A, 24A increases gradually at its right-hand end and decreasesgradually at its left-hand end, as viewed in FIG. 2.

The main portion of the hollow cylindrical stator 20 has a first orrearmost set of apertures 27 (see particularly FIG. 4) which are nearestto the feed screw 1, a second set of apertures 28 which are smaller thanthe apertures 27, a third set of apertures 29 which are preferablysmaller than the apertures 28, and a fourth set of apertures 30 whichare smaller than the apertures 29 and are remotest from the feedscrew 1. The apertures 27, 28 and 29, 30 respectively surround therecesses 23, 24 of the cylindrical rotor body 21A. The guide member 17has two internal (ring-shaped) partitions 17a, 17b which respectivelyengage the periphery of the stator 20 between the apertures 27, 28 and29, 30. The apertures of each set of apertures in the main portion ofthe stator 20 may form one or more annuli; they may be staggered withrespect to each other, as considered in the circumferential and/or axialdirection of the rotor 21; they may be bounded by cylindrical orotherwise configurated surfaces; they may extend radially of or at anoblique angle with respect to the axis 22; and they may but need not beof identical size and/or shape. For example, the apertures 27 mayinclude apertures having circular or polygonal outlines as well asrelatively large and relatively small apertures all of which arepreferably larger than the apertures 28. Also, the apertures 27 may beoval whereas the apertures 28, 39 and/or 30 are round or polygonal, orvice versa.

The guide 17 defines with the right-hand end portion of the stator 20 aring-shaped intake 42 which receives kneaded and homogenized materialfrom the adjacent outlet of the barrel 12 and from which the materialcan enter the cells 23A by passing through the apertures 27. The intake42 terminates at the right-hand partition 17a of the guide 17. Themedian portion of the guide 17 (between the partitions 17a, 17b) defineswith the median portion of the stator 20 a ring-shaped intermediatepassage 43 which can receive material from the cells 23A via apertures28 and can admit material to the cells 24A via apertures 29. Thering-shaped outlet 44 between the left-hand end portions of the guide 17and stator 20 receives material from the cells 24A via apertures 30 anddischarges material into the channel 3a via openings 20c in the collar20b.

The extruder 4 of the crumb-forming unit D is removably installed in thesupport 9 at the lower end of the channel 3b. It has holes 19 whichdischarge material downwardly into a funnel 310 forming part of ahousing 317 in the drier E. Strands of material issuing from the holes19 are severed by blades 57 forming part of the unit D and being mountedon the vertical output shaft 55 of an electric motor 56. The subdivisionof strands which issue from the holes 19 by the rapidly rotating blades57 results in the formation of crumbs Cr. The motor 56 is preferably ofthe variable-speed type; alternatively, the output shaft 55 can drivethe blades 57 through the medium of a variable-speed transmission, notshown. This motor can be mounted on the base 8 or another stationarypart of the apparatus, e.g., on the housing 317 of the drier E.

As stated above, the cooker A (or another suitable preconditioning unit)constitutes an optional feature of the apparatus. The same applies forthe units E and F. For example, the apparatus can be used to convertfresh (i.e. moist) banana peels into crumbs Cr which are to be consumedimmediately after they issue from the unit D. The peels (with a moisturecontent of 20-60 percent, preferably 35-55 percent) are fed directlyinto the hopper 7 of the barrel 12 by a suitable conveyor or by hand.

The motor 5 is on so that it drives the feed screw 1 and the rotor 21 ata preselected speed. The motor 56 is also started to drive the blades 57of the crumb-forming unit D. The thread or threads 11 of the core 10draw raw material into the helical path or paths 13 and force thematerial to advance toward and into the intake 42. The feed screw 1effects a highly desirable preliminary comminution and homogenization ofraw material. The feed screw 1 further insures that the material whichfills the intake 42 penetrates into the cells 23A by passing through thelargest apertures 27 of the stator 20, and such material is comminutedby the orbiting knives 25 of the rotor 21. The path of cutting edges atthe outer ends of the knives 25 is substantially normal to the directionof material flow through the apertures 27. Since the cylindrical body21A of the rotor 21 carries twelve equally spaced knives 25, each strandof material which passes through an aperture 27 is severed twelve timesduring each revolution of the feed screw 1. The material which passesthrough the apertures 27 is of pulpy or mashy consistency. Therefore,the pressure which is produced by the rotating feed screw 1 suffices toforce the material out of the cells 23A (owing to continuous inflow ofmaterial via apertures 27) whereby the material passes through theapertures 28 and is severed again by knives 25 on its way into theintermediate passage 43. The material then penetrates into the cells 24Aby flowing through the apertures 29 and is severed again by knives 25.Additional severing takes place when the material enters the outlet 44by flowing through the apertures 30. Such material then enters thechannel 3a by way of openings 20C in the collar 20b of the stator 20.When the channel 3a is full, it begins to discharge and force materialinto the channel 3b so that the material is compelled to pass throughthe holes 19 of the extruder 4 and is converted into crumbs Cr by therapidly rotating blades 57 of the unit D.

The extent to which the material being fed into the hopper 7 of thebarrel 12 will be comminuted can be determined in advance by appropriateselection of the size of apertures 27-30 in the stator 20, thecross-sectional area of the path 13, the RPM of the feed screw 1 androtor 21, the pressure which the feedscrew 1 exerts upon the materialfilling the intake 42 (i.e., the speed at which the material flowsthrough the apertures 27-30), the number of knives 25, the number ofapertures 27, 28, 29 and/or 30, and the length of the barrel 12. Otherparameters which determine the extent to which the material iscomminuted on its way from the hopper 7 into the channel 3a include thenature of starting material (e.g., banana peels or grains or kernels ofwheat, corn or the like) and the moisture content of starting material.As a rule, the comminuting action progresses during each passage ofmaterial into the interior of or from the apertured stator 20.

The energy requirements of the apparatus, when utilized for theconversion of fresh banana peels into crumbs Cr, are surprisingly low.Such low energy requirements of the apparatus are attributable, at leastto a substantial degree, to the fact that it is much simpler and easierto comminute a moist or wet vegetable than a dried vegetable. It isclear that the crumbs can be thereupon dried, in one or more stages, andground to yield banana peel flour or farina. The term "farina" isintended to denote granular products whose size exceeds that of productswhich are commonly known as flour. The drying can be carried out in theunit E or in an analogous drier, e.g., a drier which withdraws moisturefrom crumbs Cr in two or more stages one (preferably the first) of whichincludes vibrating, shaking or otherwise agitating the crumbs to insuremore satisfactory contact between all sides of each crumb and hot air oranother moisture withdrawing medium.

The shape of the crumbs which are produced in the apparatus of thepresent invention can be said to resemble that of pellets of the typeoften used as animal fodder or that of minced or chopped meat cubes.However, the consistency of crumbs is somewhere (and often exactly)between that of a meat cube and that of a pellet of animal fodder. Thus,a meat cube normally consists of a few pieces of comminuted meat whichare still sufficiently large to be readily discernible with naked eye.On the other hand, a pellet of the type often used as animal fodderoften consists of an extremely large number of minute fragments whosesize is equal to or approximates that of flour or farina particles andwhich are compacted or condensed to form a self-sustaining body known aspellet. The minute particles of a pellet cannot be readily discernedwith naked eye.

The crumbs which issue from the unit D can contain relatively largefragments, e.g., fragments whose maximum dimensions range between 1-2millimeters, normally between 1-11/2 millimeters. The fragments adhereto each other and are normally of different size and/or shape. Forexample, the fragments may include differently dimensioned and/orconfigurated particles of shells or husks of grains whose moisturecontent is relatively high and which are partially bonded to each otherby a viscous (pasty) substance. The crumbs Cr can readily accept andretain additional moisture and can readily release moisture. The crumbsissuing from the unit D are comparable to bread crumbs, earth crumbs orthe like. The ability of crumbs to release substantial quantities ofmoisture in response to drying is important and desirable, especially ifthe crumbs are to be converted into flour or farina.

The consistency of certain vegetables which are treated in the units A,B, and C or in the units B and C is such that they will form discretecrumbs without resorting to a severing action. Thus, the conversion ofmaterial which fills the channel 3b into discrete crumbs can beeffected, at least in some instances, without resorting to the severingmeans including the blades 57. Severing of material which issues fromthe holes 19 of the extruder 4 is desirable when the material contains ahigh percentage of moisture. Such severing insures that the size and/orshape of all or nearly all crumbs equals or approximates a desirablenorm which is best suited for subsequent drying and grinding. Owing tothe high porosity of crumbs, they can be readily relieved of surplusmoisture by resorting to relatively simple and inexpensive driers, suchas the drier E which comprises a single endless conveyor 312. Theaforementioned multi-stage drying will be resorted to when the crumbsare very wet so that they are likely to adhere to each other. The firststage then peferably comprises agitating the crumbs in a suitable shakeror the like to effect rapid removal of such quantities of moisture whichwould cause the freshly formed crumbs to adhere to each other.

Referring again to FIG. 1, the cooker A comprises a suitable vessel 300having a drain pipe 301 in or close to the bottom wall thereof. The pipe301 contains a shutoff valve 301A. The vessel 300 has twin walls 302defining one or more paths for the circulation of steam, hot water oranother suitable heating medium. The material to be cooked, (e.g.,freshly harvested corn Co) is fed by way of a supply pipe 303 (or achute, not shown) which preferably receives material from a mainmagazine (not shown) through a suitable metering device. Water can besupplied by a pipe 304 containing a shutoff valve 304A. When thepreconditioning of material in the vessel 300 is completed, the pump 305is started to feed such material into the hopper 7 by way of the conduit306.

The drier E comprises the aforementioned housing 317 with funnel 310which receives crumbs Cr from the unit D. The housing 317 confines andsupports two spaced-apart sprocket wheels 316 for the endless chainconveyor 312 which is assembled of normally interlaced S-shaped links313. The upper reach 325 of the conveyor 312 travels below the funnel310 to receive and entrain the crumbs Cr in a direction to the right, asviewed in FIG. 1. The lower reach 324 receives partially dried crumbs Crimmediately downstream of the right-hand sprocket wheel 316 and deliversdried crumbs to a funnel 318 having a discharge opening 319 above therolls 330 of the mill F. The rolls 330 convert dried crumbs Cr intoflour or farina Fl which descends into a collecting funnel 331.

The left-hand sprocket wheel 316 is driven by a coaxial pulley orsprocket wheel 315 which receives motion from the output element of adiscrete electric motor 314 (preferably a variable-speed motor) mountedon the housing 317. The links 313 of the upper reach 325 are caused topivot immediately upstream of the right-hand sprocket wheel 316 todischarge partially dried crumbs Cr onto the lower reach 324, and thelinks 313 of the lower reach 324 are caused to pivot immediatelyupstream of the left-hand sprocket wheel 316 to discharge dried crumbsCr into the funnel 318. Conveyors using such or similar types of linksare known in the art of food processing. The major part of the upperreach 325 forms a relatively wide air-permeable band which transports alayer of crumbs toward the right-hand sprocket wheel 316, and the majorpart of the lower reach 324 forms a similar air-permeable band whichtransports a layer of crumbs toward the funnel 318. Heated air isadmitted into the lower portion of the housing 317 (below the lowerreach 324) by way of a duct 320, and spent air is evacuated from theupper portion of the housing 317 (above the upper reach 325) by asuction fan 322 mounted in a duct 321. The arrows 323 indicate thedirection of flow of hot air currents through the lower reach 324 of theconveyor 312, through the space 307 between the reaches 324, 325,through the upper reach 325, and toward and into the duct 321. Each link313 which approaches the right-hand or left-hand sprocket wheel 316 istemporarily tilted or pivoted by a suitable cam or the like, not shown,so that the thus tilted links then form a number of gaps through whichthe crumbs respectively descend from the upper reach 325 onto the lowerreach 324 and from the lower reach 324 into the funnel 318.

The means for rotating the rolls 330 of the mill F is not shown in thedrawing. It is clear that the mill F may comprise two or more passes ofcomminuting rolls.

The exact design of the cooker A, drier E and/or mill F will depend on anumber of factors, such as the nature of material to be treated, theextent to which the moisture content of crumbs should be reduced priorto grinding, the desired output per unit time, the fineness of the finalproduct and/or others.

In its simplest form, the unit C may comprise a device similar to a meatgrinder wherein a stationary apertured disk is adjacent to one or morerotary cutters which sever strands of material passing through theapertures or sever the material in front of the disk. However, a hollowcylindrical stator with a rotor therein is preferred in most instances,especially since the material to be severed by the knives of the rotorcan be caused to repeatedly enter into and issue from the stator.Moreover, the wear upon a hollow cylindrical stator and upon a rotorwhich is at least partially confined in the stator is much lesspronounced than the wear upon the stationary and mobile cutting parts ina conventional meat grinder. A hollow cylindrical stator and/or a rotorin such stator is not subjected to excessive axial stresses; inaddition, all radial stresses are equally distributed along thecircumference of the stator, i.e., such radial stresses normally balanceor neutralize each other. The number of knives is normally between 10and 15; however, it is equally possible to operate with fewer knives(e.g., eight) or more than 15 knives. A large number of relatively smallknives can be accommodated in a small area. A hollow cylindrical statoris preferred on the additional ground that it allows for repeatedhomogenization of material subsequent to each pass across the path ofthe orbiting knives. A substantial part of the homogenization takesplace in the ring-shaped inlet, intermediate passage and outlet betweenthe stator and the guide member.

If the ultimate product Fl is flour or farina which is to be used forthe baking of tortillas, the apparatus of FIG. 1 is operated as follows:

Dried grains of corn (maize) are admitted into the vessel 300 with acustomary amount of lime and water,* and are cooked for about 50minutes, normally less than 60 minutes. During cooking, the mass of cornshould be constantly covered with water, i.e., the upper surface of thebody of water in the vessel 300 should not be below the level of theupper stratum of corn. After cooking for 50 minutes, the valve 304A isopened so that the pipe 304 admits a metered quantity of water,preferably about 1/4-liter per kilogram of corn. The mass is thereuponstirred and the valve 301A is opened to allow for evacuation of thatquantity of water which has been admitted via pipe 304. The admission ofwater via pipe 301, stirring of the mass subsequent to such admission,and the evacuation of thus admitted water via pipe 301 results indesirable rinsing of corn. However, the rinsing could not be toopronounced in order to avoid the evacuation of excessive quantities ofviscous or slimy ingredients which consist primarily of chalk.

The freshly cooked and rinsed but still quite hot mass is thereupon fedinto the hopper 7 by the pump 305, preferably while the mass contains40-60 percent, more preferably in excess of 50 percent and mostpreferably about 52-54 percent of moisture. In accordance with a highlyadvantageous feature of the method, the grains of corn Co which areadmitted into the barrel 12 via hopper 7 undergo a very intensivekneading action. The internal surface of the barrel 12 is preferablyprovided with shallow longitudinally extending grooves 12M (shown inFIG. 2) which enable the feed screw 1 to advance the mass toward theunit C. Moreover, the internally grooved barrel 12 cooperates with thethreads 11 to effect a highly satisfactory, pronounced and desirablecomminution or fragmentizing of corn Co. Also, the just discussedpressing, fragmentizing and kneading results in pronounced initial orpreliminary homogenization of cooking particles. The length of thebarrel 12 should be sufficient to insure that the rotating feed screw 1will produce a pressure of several kilograms per square centimeter. Thewidth of the path 13 is assumed to be 3-13 millimeters (as considered inthe radial direction of the barrel 12). The aforementioned pressure isdesirable in order to insure intimate mixing of chalk-containing viscoussubstances with fragments of corn whereby the viscous substances reactwith or otherwise affect the condition of the fragments. The mixing ofchalk with fragments of corn in the barrel 12 is desirable because thisis the most satisfactory locus for homogenization (i.e., for uniformdistribution of chalk in the mass of comminuted corn). In other words,if the viscous substances are not intimately mixed with and uniformlydistributed among the fragments of corn during travel along the path orpaths 13, the ultimate product Fl is unlikely to contain corn and chalkin uniform distribution.

It has been found that the taste of tortilla flour is much lesssatisfactory if the treatment in the unit B is omitted or replaced witha different treatment. Thus, and assuming that, instead of beingkneaded, homogenized, compressed and comminuted, cooked corn Co which asbeen removed from the vessel 300 is comminuted in a different way, thetaste of flour which is obtained by thereupon conveying theconventionally comminuted grains of cooked corn through the units C-F ofthe apparatus of FIG. 1 will be much less satisfactory than if the unitC receives comminuted, homogenized and kneaded material from the unit B.

The mass which issues from the barrel 12 is thereupon treated in thesame way as described above in connection with the making of crumbs frombanana peels, and the crumbs are introduced into the drier E. Themincing unit C can be modified and/or simplified in a manner to bedescribed in connection with FIGS. 5-8; however, in each instance, themincing unit preferably causes the material to undergo at least twosevering actions, i.e., the rotor of the mincing unit should have atleast two sets of apertures the first of which enables strands ofmaterial to enter a set of cells and the other of which allows strandsof material to issue from the cells whereby the strands are severedduring entry into as well as during flow out of the cells.

It is further desirable to bring about a pronounced homogenizationsubsequent to each severing step. With reference to FIGS. 1-4, thismeans that the body 21A of the rotor 21 should have relatively largecells 23A, that the guide member 17 and the stator 20 should define arelatively large passage 43, that the body 21A should have relativelylarge cells 24A, and that the member 17 should define with the stator 20a relatively large outlet 44. Thus, ample room should be provided formixing of fragments of corn subsequent to each severing by the knives25. Homogenization of material during severing by the knives 25 isfurther enhanced by providing the stator 20 with relatively largeapertures. Highly satisfactory results can be obtained if the stator hasat least three sets of apertures including largest apertures with adiameter of approximately 5 millimeters, medium-sized apertures with adiameter of about 3 millimeters, and smallest apertures with a diameterof about 2 millimeters. The diameters of the crumbs Cr are preferably inthe range of 5 millimeters. If the crumbs are short cylinders, theirlength preferably equals or approximates their diameter.

The drier E (or another suitable drier) is preferably designed to reducethe moisture content of crumbs Cr from 52-54 percent to about 10 percentwithin a period of 20-120 minutes. The conversion of dried crumbs intoflour or farina Fl can be effected by resorting to a customary flourmill, to ball mills or other impact-type mills which are capable ofreducing the crumbs to a desired degree of fineness.

Flour or farina Fl which issues from the unit F can be used for thebaking of tortillas or similar products whose quality matches or exceedsthat of tortillas made on a small scale in accordance with traditionalprocedures. This is achieved by converting corn Co and customaryadditives first into crumbs Cr, by thereupon drying the crumbs, and bythereupon comminuting the crumbs in the unit F of FIG. 1 or in ananalogous unit. The making of flour or farina may be continuous orintermittent.

The unit A can be omitted in its entirety if the feed screw 1 is longenough to insure heating to boiling or cooking temperature during travelof corn from the hopper 7 into the unit C. Also, the cooking of corn canbe effected partly in the vessel 300 and partly in the barrel 12.

Flour or farina which is obtained from corn Co is mixed with water andformed into thin round cakes having a diameter of 10-15 centimeters.Such cakes are thereupon baked and consumed without any additives,converted into cones and filled with meat, sauces or the like, dippedinto one or more sauces, or coated with one or more sauces or the like.Tortillas or enchiladas are consumed in many Latin American countriesinstead of bread. An acceptable tortilla must exhibit a characteristictaste and color. Furthermore, it must be readily shaped without breakingor tearing. Moreover, flour or farina which is used for the making ofsatisfactory tortillas must be capable of taking up substantialquantities of moisture.

Heretofore known attempts to mass-produce tortilla flour or farina fromdried corn have failed because the product did not exhibit theafore-discussed desirable characteristics which are expected byconsumers of such exotic foods. It was already proposed to cook or boildried corn grains in the presence of water and chalk. The thus obtainedproduct is thereupon rinsed and immediately introduced into an impacttype mill together with a quantity of dried corn because an impact millcannot comminute a highly viscous substance of pasty or likeconsistency. The material which issues from the impact mill is thereupontreated in a thermopneumatic drier, subjected to a renewed grinding orcomminuting action, and ultimately sifted. Such method can be resortedto for the making of reasonably acceptable tortilla flours; however, itis not sufficiently economical to allow for the making of tortilla flouror farina at a cost which is sufficiently low to warrant its use indeveloping countries of Latin America and elsewhere. Furthermore, thewear upon component parts of the apparatus for the practice of suchconventional method is very high, and this is attributable largely tothe fact that cooked material must be mixed with dry corn prior toadmission into and treatment in the impact mill. Extremely largequantities of heat energy are necessary for repeated drying of theproduct, namely for drying of material which is to be cooked, for dryingthe material which is to be added to cooked material prior to admissioninto the mill, and for drying of material which is discharged from themill. Still further, even though the flour or farina which can beobtained in accordance with the just discussed method is acceptable, itsquality is invariably inferior to that of flour or farina which is beingproduced in Mexico and other Latin American countries in accordance withtraditional (small scale) procedure which the children learn from theirparents. Such traditional procedures involve kneading of cooked corn,i.e., a step which is lacking in the aforediscussed conventional method.

Experiments with farina or flour which is produced in accordance withour method and by resorting to apparatus of the type shown in FIGS. 1-4have produced results which surpassed the most optimistic expectations.Thus, tortillas made from such flour or farina are of surprisingly highquality, especially as regards their taste and appearance. Moreover, themethod is economical because it does not involve recirculation of anyvegetables so that the output of the apparatus is high and its energyrequirements low. The apparatus can be used for continuous production ofcrumbs and/or flour or farina, especially if the unit A comprises two ormore vessels so that the contents of one vessel are being transferredinto the hopper 7 while the material filling the other vessel or vesselsis being cooked, and vice versa.

The treatment of grains or the like in the unit B constitutes a veryimportant and advantageous step of the improved method of making crumsCr or a flowable mass of smaller particles Fl. Thus, the kneading ofgrains in the barrel 12 causes release of a relatively small percentageof liquid and viscous substances simultaneously with comminution ofcellular parts, such as husks or shells and kernels whereby thecomminuted cellular parts form a composite mass whose consistency isbasically different from that of starting materials. Thus, the mass ismuch looser than the coherent portions of a moist grain or the like.

The apparatus of the present invention preferably seals the material ormaterials to be treated from the surrounding atmosphere, at least duringtravel of materials from the hopper 7 to the drier E. The force(pressure) which is needed to maintain the foodstuffs in motion duringtravel from the hopper 7 to the inlet of the drier E is preferablysupplied exclusively by the rotating feed screw of the unit B.

Many types of vegetable foodstuffs can be processed in apparatus whereinthe feed screw 1 produces a static pressure in the range of from afraction of one kilogram to a few kilograms per square centimeter. Thestatic pressure which is best suited for treatment in the unit B dependsalso on the desired degree of comminution of a particular foodstuff andon intended use and size of the ultimate product (i.e., crumbs, flour orfarina). It has been found that quite a few foodstuffs can be treated byresorting to extremely low static pressures. On the other hand, manyfoodstuffs must be processed at pressures of 20, 30 and more kilogramsper square centimeter. This necessitates the utilization of a relativelylarge and long feed screw. The feed screw of the unit B is differentfrom and superior to the feed screws of conventional meat grindingmachines which produce a minimum of or no kneading action at all, whichcannot establish and maintain relatively high static pressures, andwherein the material which is being comminuted (or is about to becomminuted) is fed through relatively short distances in a small numberof channels or paths having large cross-sectional areas.

If a particular foodstuff must undergo a very pronounced homogenizingaction prior to entry into the mincing unit C, the unit B willpreferably employ a feed screw whose core has a very large diameter, ascompared with the internal diameter of the barrel. This guarantees thatthe parts 1 and 12 will define one or more narrow paths wherein thematerial is not only comminuted and homogenized but is also subjected tovery high pressures which insure that the material will pass throughrelatively large as well as through relatively and extremely smallapertures of the stator 20.

The apparatus of FIG. 1 can be used with advantage for processing offoodstuffs which must undergo a very pronounced comminuting as well as avery intensive homogenizing action, i.e., of foodstuffs which cannot behomogenized to a desired extent exclusively during travel in the path orpaths defined by the barrel 12 and feed screw 1. Thus, additional andvery pronounced homogenization must take place in the mincing unit Cwhich is designed to insure thorough intermixing of all ingredientssimultaneously with an equally thorough comminuting action. The extentof homogenization and the extent of comminution in the mincing unit Cwill depend on the number of times the material is being extrudedthrough the apertures of the stator 20 and severed by the knives 25 ofthe rotor 21. Such repeated and frequent severing and honogenizinginsures intimate intermixture of pulpy or similar substances with water,other additives (such as chalk) and solid particulate material. Asmentioned above, additional homogenization is effected as a result ofrepeated accumulation of material in ring-shaped spaces including theintake 42, passage 43, outlet 44, recess 23 and recess 24. Thus, as thematerial which fills the intake 42 enters the cells 23A of the recess23, it is subdivided into a very large number of strands which areforced to flow through the apertures 27 and are severed, at veryfrequent intervals, by the rapidly orbiting knives 25 of the rotor 21.The thus formed and severed strands accumulate in the respective cells23A to form batches of thoroughly intermixed ingredients, and suchbatches are thereupon extruded through the apertures 28 withsimultaneous repeated severing by the knives 25. The repeatedly severedstrands which enter the passage 43 accumulate into a batch ofhomogeneous ingredients, and such batch is extruded into the cells 24Awith simultaneous frequent severing, and so on. Consequently, the masswhich fills the channel 3b consists of intimately intermixedingredients. The homogenizing action of the mincing unit C is furtherenhanced by repeated changes in the direction of material flow on itsway from the path or paths 13 into the channel 3b. Such material flowsin part axially, in part circumferentially and in part radially inwardlyor outwardly of the rotor 21 whereby its ingredients undergo additionaldesirable and thorough homogenizing action. Still further homogenizationtakes place when the material which accumulates in the outlet 44 flowsthrough the openings 20c, is thereupon deflected by the channel 3a,accumulates in the channel 3b, and passes through the holes 19.

For proper treatment of a majority of foodstuffs, the diameters Xa ofholes 19 in the extruder 4 should at least equal but preferably exceedthe diameters of smallest apertures in the stator 20 (it being assumedthat the holes 19 and apertures 30 are circular). However, this does notmean that each crumb Cr consists of, say, two or four discrete parts orfragments. The diameters of apertures in the stator 20 establish purelytheoretical standards for the dimensions of largest fragments orparticles which enter the channel 3a. As a rule, the major part of eachpiece of foodstuff (e.g., a grain or peel) is subdivided into fragmentswhose maximum dimensions are much less than the maximum dimensions ofapertures in the stator. This is due to the fact that the maximumdimensions of fragments are also influenced by the RPM of the rotor 21,the number of knives 25 and/or the velocity at which the material passesthrough the apertures of the stator. It is presently preferred to designthe units C and D in such a way that the combined cross-sectional areaof the last set of apertures (30) in the stator is less than thecombined cross-sectional area of holes 19 in the extruder 4. Such designis of particular importance in connection with the processing of allsuch vegetable foodstuffs which, prior to treatment in the unit A or B,do not exhibit a pronounced porosity. Otherwise, the crumbs Cr which areformed by severing the strands passing through the holes 19 wouldresemble pellets of the type used as animal fodder or fragments of pastythreads.

As a rule, the combined cross-sectional area of holes in the extruderwill be at least twice, and preferably at least four times, the combinedcross-sectional area of the set of smallest holes in the stator of themincing unit. This insures that the maximum dimensions of fragments inthe material filling the channel 3b do not exceed the radius of a hole19. It is further preferred to greatly reduce the speed of forwardmovement of material immediately or shortly ahead of the unit D. Thus,the speed at which strands of comminuted material pass through the lastset of apertures 30 in the stator 20 should be a small fraction of thespeed at which the strands pass through the holes 19 of the extruder 4.The area of the extruder 4 is preferably several times (most preferablyat least four times) the cross-sectional area of the feed screw 1.

If the starting material is heated (e.g., in the vessel 300 of the unitA), it is preferred to convey the material through the units B, C and Dwhile the material and/or its fragments are still hot.

The distribution of holes 19 in the extruder 4 is preferably selectedwith a view to insure that the strands of homogenized materialdescending below the extruder 4 into the range of orbiting blades 57 aresufficiently spaced from each other, i.e., that the freshly formedcrumbs Cr cannot or are not likely to contact each other. In manyinstances (especially if the material passing through the extruder 4contains a very high percentage of moisture), the distance between thecenters of neighboring holes 19 will be two, three or more times thediameter of a hole.

The provision of a unit B which repeatedly subdivides the materialcoming from the barrel 12 into batches or strands and repeatedly severssuch batches or strands is often desirable and advantageous because thecomposition of ultimate products (Cr or Fl) is more predictable and alsobecause the vegetables are less likely to be shredded or otherwisecomminuted in a random fashion. In many instances, it suffices if thetransport through the last set of apertures in the stator results incomminution of vegetables into fragments having maximum dimensions inthe range of 1-2 millimeters; however, the majority of fragments will bemuch smaller. Such fragments can be homogenized and converted intosatisfactory crums by passing through holes 19 having a diameter of upto 5 millimeters, preferably between 2 and 5 millimeters.

In each or nearly each instance, the crumbs Cr should have a highlyporous texture, i.e., they should consist of loosely joined fragmentswith a large number of interstices, cavities or the like to facilitaterapid and uniform drying in the unit E or an analogous unit. Such looseand porous texture is practically assured if the combined area of allholes 19 exceeds the combined area of all apertures 30, even if thestarting material exhibits negligible porosity. The porosity of crumbsCr is further enhanced due to the fact that each such crumb consists ofseveral fragments having widely different sizes and/or shapes so thatthey cannot and are not compacted or assembled into a substantiallysolid body or mass. The pressure in the channels 3a and 3b need not andpreferably is not very high; this insures that the just discussedfragments are not compressed to form solid or practically solid strandswhich would yield pellets or pasty cylinders rather than porous crumbs.

The apparatus can be used for immediate processing of freshly harvestedor collected vegetable foodstuffs or for processing of foodstuff whichhave undergone a pronounced drying or moisture-expelling action and mustbe subjected to a preliminary treatment (such as cooking in the vessel300) before they assume a consistency which is best suited forintroduction into and kneading as well as other treatment in the unit B.In many instances (or in a majority of instances), the crumbs Crconstitute intermediate products, i.e., they are thereupon relieved ofexcess moisture prior to undergoing a further comminuting action in theunit F or a similar unit. Relatively wet crumbs can be used in certaininstances as animal fodder. The making of tortilla flour or farina fromcorn in an extremely simple, time-saving and economical mannerconstitutes one of the presently preferred uses of the improved methodand apparatus.

FIG. 5 shows a modified mincing unit C₁ which receives partiallyhomogenized material from a kneading unit similar to or identical withthe unit B of FIGS. 1-2, FIG. 5 merely shows the feed screw 1, thebarrel 12 and a helical path 13. The axis 22 of the feed screw 1 isnormal to and intersects the vertical axis 100 of a rotor 101 formingpart of the mincing unit C₁. The rotor 101 is mounted in a hollowapertured cylindrical stator 102 which is surrounded by a stationarytubular guide member 103. The rotor 101 is driven by a separate primemover 5' which transmits torque to the upwardly extending shaft 110 ofthe rotor. The shaft 110 extends upwardly from and beyond the guidemember 103 and is mounted in an antifriction roller bearing 111. Theinner race of the bearing 111 is disposed above a ring-shaped seal 112for the shaft 110 which prevents liquids and/or comminuted solid matterfrom escaping into and beyond the bearing. The prime mover 5' ispreferably a variable-speed electric motor or a constant-speed motorcombined with a variable-speed transmission. The rotor 101 furthercomprises a solid cylindrical body 101A which is connected with theshaft 110 by a conical intermediate portion 113.

The upper end portion of the guide member 103 is bolted or otherwisesealingly secured to a flange of the barrel 12 and defines a suitablyconfigurated channel 114 which guides the material issuing from thekneading unit into a ring-shaped intake 115 surrounding the upper endportion of the stator 102. The configuration of the channel 114 ispreferably such that the guide member 103 does not exhibit any deadcorners for accumulation of material which is to be conveyed into thecrum-forming unit D₁. The guide member 103 has two internal ring-shapedpartitions 103a, 103b, which sealingly engage the adjacent portions ofthe peripheral surface of the stator 102. The partition 103a separatesthe intake 105 from a ring-shaped intermediate passage 116, and thepartition 103b separates the passage 116 from a ring-shaped outlet 117.The body 101A of the rotor 101 has an upper annular recess 120 and alower annular recess 121. These recesses are subdivided into annuli ofcells by vertical knives 101B which are mounted in the body 101A in amanner similar to or identical with that described in connection withthe knives 25 of FIG. 3.

The main portion of the stator 102 has an uppermost set of relativelylarge apertures 122 which admit material from the intake 115 into thecells of the recess 120, a set of smaller apertures 123 which admitmaterial from the cells of the recess 120 into the passage 116, a set ofapertures 124 which may be equal to or smaller than the apertures 123and admit material from the passage 116 into the cells of the recess121, and a set of smallest apertures 125 which admit material from thecells of the recess 121 into the outlet 117. The lower end portion 102aof the stator 102 has a collar 130 with openings 131 which allowmaterial to flow from the outlet 117 into a channel 140 defined by adiffusor-like upright support 132 for the platelike or disk-shapedextruder 134 of the unit D₁. The end portion 102a receives a frictionbearing or sleeve bearing 133 for the lower end portion of the rotor101. The upper end portion of the support 132 is sealingly secured to aflange at the lower end of the guide member 103 by bolts and nuts 132aof analogous fastener means.

The extruder 134 is removably mounted in the lower end portion of thesupport 132 by means of screws or the like, not shown, and has holes138. The distance X between the centers of neighboring holes 138 isgreater than the distance Xa between the centers of neighboring holes 19in the extruder 4 of FIG. 2. The manner in which the extruder 4 or 134is separably affixed to the respective support may but need not be thesame as known from conventional household meat grinders.

The underside of the extruder 134 is located immediately above the pathof orbiting blades 137 on the output shaft of a discrete motor 136having a vertical axis 135. The blades 137 sever the material issuingfrom the holes 138 to form crumbs Cr. For example, the output shaft ofthe motor 136 can carry three equally spaced blades 137.

The operation of apparatus which embodies the units C₁ and D₁ of FIG. 3is analogous to that of the apparatus shown in FIGS. 1-4. Thus, kneadedand homogenized material which issues from the helical path or paths 13fills the channel 114 and intake 115 to be forced into the cells of therecess 120 by way of the apertures 122 whereby the strands of materialpassing through the apertures 122 are severed by the knives 101B on therapidly rotating body 101A. The knives 101B sever the material againduring travel through the apertures 123 (into the passage 116), duringtravel through the apertures 124 (into the cells of the recess 121) andduring travel through the apertures 125 (into the outlet 117).

The diameter of the channel 140 in the support 132 increases in adirection from the outlet 117 toward the extruder 134. The upper end ofthe channel 140 receives material from the outlet 117 through theopenings 130a of the collar 130. The diameters of the holes 138 greatlyexceed the diameters of lowermost apertures 125 in the main portion ofthe stator 102 (this also applies for the apertures 30 and holes 19shown in FIG. 2). If desired, the extruder 4 or 134 may be a rectangularplate with two shorter sides (as considered in a direction from the leftto the right in FIG. 2 or 5) and two longer sides (as considered atright angles to the plane of FIG. 2 or 5). The dimensions of theextruder will be selected with a view to insure an optimum formation ofcrumbs Cr.

An important advantage of the mincing unit C₁ is that the speed of therotor 101 can be selected and regulated independently of the speed ofthe feed screw 1, or vice versa. Also, the apparatus occupies less floorspace because the axis 100 is vertical. The superior versatility of themincing unit C₁ and greater compactness of the apparatus embodying thismincing unit more than compensate for the cost and energy requirement ofthe prime mover 5'.

The unit C₁ can be used with advantage when the moisture content ofvegetables is very high. The unit D or D₁ is preferably designed todischarge crumbs downwardly, irrespective of whether the axis of therotor in the preceding unit C or C₁ is horizontal or vertical; suchorientation of the unit D and D₁ is especially advantageous when thevegetables have a high moisture content because the crumbs which areformed below the extruder 4 or 134 are less likely to contact each otherimmediately after severing of corresponding strands by the orbitingblades 57 or 137.

The provision of a separate prime mover (5') for the rotor of themincing unit is particularly advantageous and desirable if the apparatususing such mincing unit is to be used for processing of a wide varietyof vegetable foodstuffs.

Those apertures of the stator in the unit C or C₁ which admit materialinto the interior of the stator are preferably larger than the apertureswhich allow material to pass from the interior of the stator into thepassage or outlet between the stator and the guide member. This insuresthat the resistance which the material offers to flow into and out ofthe stator is relatively low, i.e., the feed screw 1 can be made shorterbecause it need not produce a high pressure. In many instances, thewidth of the path or paths 13 should not exceed 10 millimeters andshould not be less than 3 millimeters, and the entire path or pathsshould not take up more than 30 percent of the interior of the barrel,preferably not more than 25 percent. Such dimensioning of the feed screwand barrel insures that the unit B produces a pronounced kneadingaction.

FIG. 6 shows a simplified mincing unit C₂. The rotor 200 has a threadedstub 201 in a tapped bore of the feed screw 1, and its peripheralsurface is formed with a single annular recess 207. The stator 202 is arelatively short cylinder which surrounds approximately one-half of therotor 200 and has a single set of apertures 203. The tubular guidemember 204 is mounted in a sleeve 208 which is secured to a barrel 210for the feed screw 1. The knives 200B subdivide the recess 207 into anannulus of cells whose outer sides are open so that they can receivematerial from the ring-shaped intake 205 and can discharge material intoa ring-shaped outlet 206 whereby such material passes through theapertures 203 and is severed by the knives 200B. The guide member 204has a single ring-shaped partition 204a which engages the periphery ofthe right-hand end portion of the stator 202. The partition 204aprevents direct flow of material from the intake 205 into the outlet206, i.e., the material must flow through the cells of the recess 207and through the apertures 203. The depth of each cell increases in adirection from the feed screw 1 toward the nearest end of the stator 202and decreases toward the left-hand end of the rotor 200.

The left-hand end of the sleeve 208 is connected with a plate-likeholder 209 which performs the function of the collar 20b or 130 and hasopenings 209a for admission of material from the outlet 206 into achannel immediately upstream of the extruder, not shown. The stator 202is rigid with the holder 209 and/or guide member 204, and the latterabuts against the left-hand end of the barrel 210.

Apparatus which embody mincing units of the type shown in FIG. 6 areespecially suited for processing of elongated and/or fibrous vegetables,such as fresh and hence moist banana peels. The peels are subjected toan intensive comminuting action in the interior of the barrel 210, andthe comminuting action is completed during travel from the intake 205into the outlet 206. Since the peels are elongated, the thread orthreads 11 can force them into the intake 205 without resorting toelevated pressures, and the apertures 203 convey large quantities ofcomminuted peels into the outlet 206 whereby the material passingthrough the apertures 203 is subjected to repeated severing action ofthe knives 200B.

The unit C₂ is suited for comminution of relatively tough vegetablefoodstuffs, e.g., such as the aforementioned foodstuffs having anelongated shape and longitudinally extending fibres. These foodstuffscan enter the interior of the stator 202 without passing through a setof apertures, i.e., they are severed by knives 200B only while they passfrom the interior of the stator into the outlet 206. The feature thatthe recess or recesses of the rotor in the mincing unit are deepest inthe central regions and shallower at the receiving and discharging endsthereof is desirable and advantageous because such design reduces theresistance which the material offers to the flow into and from therespective cells; this, in turn, insures that the apparatus can operatewith a relatively short feed screw. Moreover, the severing action ismore uniform if the material offers a predictable resistance to flowinto and from the cells of the rotor. Still further, such design of therecess or recesses in the rotor insures a desirable self-cleaningaction, at least while the apparatus is in use. Also, the likelihood offormation of dead corners is reduced or eliminated so that each fragmentof each piece of vegetable which is introduced into the hopper 7 remainsin the interior of the composite housing (including the barrel, sleeveor guide member and connecting member) for a predetermined interval oftime.

The features of the mincing units C and C₂ or C₁ and C₂ can be embodiedin a single mincing unit. Thus, the stator 20 of FIG. 2 can be madeshorter and its apertures 27 omitted. The partition 17a then sealinglyengages the right-hand end of the thus modified stator. Material issuingfrom the outlet of the barrel 12 and flowing into the intake 42 canimmediately enter the right-hand portions of the cells 23A to be severedprior to passing outwardly through the apertures 28, to be again severedprior to entering the cells 24A by way of the apertures 29, and to besevered for a third time prior to entering the apertures 30 on its wayinto the outlet 44.

It is also within the purview of the invention to make the rotorintegral with the feed screw, i.e., the front end portion or tip of thefeed screw may constitute the rotor of the mincing unit. Such rotor maybe equipped with removable blades or it may be formed with integralblades.

It is further possible to mount the unit B in such a way that its axisis vertical. For example, if the axis of the feed screw 1 in FIG. 2 isvertical, the housing of the apparatus may comprise a suitableconnecting member (similar to the member 3) which conveys material fromthe outlet at the lower end of the barrel into the intake 42 of the unitC.

FIG. 7 shows a mincing unit C₃ which constitutes a modification of theunit C₂. The rotor 1209 has a single ring-shaped recess 1208 and issurrounded by a hollow cylindrical stator 220. The latter has two setsof apertures 221 and 222 which are separated from each other by thering-shaped internal partition 204a of the guide member 204. The knives1209B of the rotor sever the material during flow from the intake 205into the cells of the recess 1208 (while the material is forced to flowthrough the apertures 221) and again during flow from the cells into theoutlet 206 (while the material flows through the apertures 222). Thediameters of the apertures 222 are smaller than those of the apertures221. The knives 1209B may constitute integral parts of the cylindricalbody of the rotor 1209.

FIG. 8 shows a mincing unit C₄ wherein the cylindrical body of the rotor160 has a relatively long first recess 172 and a relatively short secondrecess 173. This body rotates with the feed screw 1 and carries discreteknives 160B. Thus, each of the two recesses 172, 173 is subdivided intoan annulus of cells which are open at their outer sides. The cells ofthe recess 172 register with the apertures 162, 163 and the cells of therecess 173 register with the apertures 164, 165 of a hollow cylindricalstator 161 which surrounds the rotor 160 and is rigid with a holder 240.The annular guide member of the mincing unit C₄ has two discrete coaxialsections 167, 168 which are respectively formed with ring-shapedinternal partitions 167a, 168a. The partition 167a separates an intake169 from an intermediate passage 170, and the partition 168a separatesthe passage 170 from an outlet 171. The apertures 162, 163 are disposedat the opposite sides of the partition 167a, and the apertures 164, 165are disposed at the opposite sides of the partition 168a. The apertures165, 164, 163 are respectively smaller than the apertures 164, 163, 162.The guide member sections 167, 168 are installed, end-to- end, in asleeve 166 which extends between the holder 240 and the barrel for thefeed screw 1.

FIG. 8 shows that the length AA of the recess 173 is substantially lessthan the length BB of the recess 172 (as considered in the axialdirection of the rotor 160). The partition 167a is disposedsubstantially or exactly midway between the axial ends of the recess172. However, the partition 168a is nearer to the left-hand than to theright hand axial end of the recess 173 so that the smallest apertures165 occupy a relatively short portion a and the next-larger apertures164 occupy a longer portion b of the stator 161.

In each of the mincing units shown in FIGS. 2, and 5-8, the stator ispreferably formed with one or more or groups of apertures whereby eachsuch set comprises a relatively large number of discrete apertures (seeparticularly FIG. 4). The exact number of apertures in the stator can becalculated in dependency on desired output of the apparatus and on thenature of material to be treated. Alternatively, the number of aperturesin each set of apertures can be determined empirically for two or morewidely different types of vegetable foodstuffs, and is thereupondetermined by analogy for processing of other foodstuffs. For example,if a specially designed stator has been found to be suited forcomminuting of wheat, a similar or identical stator will be used forprocessing of rye and/or corn. Analogously, if a stator has been foundto be suitable for processing banana peels, it can be used (in identicalor somewhat modified form) for processing of string beans or the like.

The reasons for resorting to different embodiments of stators inconnection with processing of different types of foodstuffs arenumerous. For example, certain foodstuffs tend to clog the apertures 162and/or 163 of FIG. 8 during the initial stage of a mincing operation.This applies particularly for foodstuffs which are readily flowable assoon as they issue from the barrel of the kneading unit, certain otherfoodstuffs (which require a longer interval of time before they becomereadily flowable) are likely to pass through the apertures 162, 163 butwill clog the smaller apertures 164 and/or 165. In the first instance,the likelihood of clogging the larger apertures 162 and/or 163 isreduced by making the recess 172 longer than the recess 173 so as toprovide more room for the apertures 162, 163. In the second instance(which is much more frequent that the first instance), the rotor bodywill be provided with two recesses of identical axial length (as shownin FIG. 2) so as to allow for the machining of large numbers of smallerapertures (such as 29, 30 of FIG. 2). Thus, the likelihood of cloggingof smaller apertures is reduced by reducing the ratio of the combinedcross-sectional area of smaller passages to combined cross-sectionalarea of larger passages, and the likelihood of clogging of largerapertures is reduced by increasing such ratio. Since the stator is ahollow cylinder, it allows for a practically unlimited number of variouscombinations of apertures as regards their size, distribution,configuration and the ratio of apertures in one set to those in theother set or sets. If one finds that a certain material will not passthrough the apertures of a relatively short hollow cylindrical stator,the stator is made longer or the recess or recesses in the rotor bodyare made longer to allow for the provision of larger numbers ofapertures having a certain size. This distinguishes the improved mincerfrom conventional meat grinders or the like wherein feed screw forcesmaterial directly against a disk similar to the extruder 4.

All that counts is to select the length, diameter, the number ofapertures in and/or other parameters of the stator in such a way thateach set of apertures will offer an optimum resistance to the flow offragmentized or partially comminuted material therethrough. As a rule,maximum resistance to flow will be offered by the last set of aperturesif the stator has two or more sets of apertures. As mentioned above, theapertures may but need not extend exactly radially of the stator; atleast some of them may be substantially or partially tangential to thestator and/or at least some of them may extend in or counter to thedirection of material flow from the interior of the guide means into theinterior of the stator or vice versa.

The diameter of the outermost part or component of the mincing unit maybut need not equal or approximate the diameter of the feed screw in theunit B. As shown in the drawing, the outer diameter of the stator mayequal or approximate the diameter of the core of the feed screw. Sincethe diameter of the core is preferably larger (e.g., 250 millimeters),the just mentioned selection of the outer diameter of the stator insuresthat the latter can be formed with a large number of apertures which maybe grouped into one, two or more sets. Still further, such dimensioningof the stator facilitates the transport of kneaded material into themincing unit.

Additional homogenization of the material can be achieved (or suchhomogenization further influenced) by subdivision of the intake,intermediate passage and/or outlet between the stator and guide memberinto two or more discrete compartments. For example, and referring toFIG. 2, the intake 42, the passage 43, and/or the outlet 44 can besubdivided into two or more arcuate compartments which are separatedfrom each other by axially extending partitions.

We claim:
 1. A method of continuously processing soft and moistvegetable foodstuffs, particularly vegetables having a high moisturecontent, comprising the steps of subjecting the moist vegetables to apronounced compressing, kneading and attendant first homogenizing actionto form a mass of fragmentized vegetables; subsequently comminuting saidmass including subdividing said mass into a plurality of smaller batchesand severing the batches to form a plurality of fragments whilehomogenizing the fragmentized material by reforming the same into acontinuous mass; and subsequently dividing the reformed continuous massinto discrete crumbs.
 2. A method as defined in claim 1, wherein saidsmaller batches are strands.
 3. A method as defined in claim 1, whereinsaid vegetables are grains of corn, and further comprising the step ofdrying said crumbs and comminuting the thus dried crumbs to form aflowable pulverulent or granular product.
 4. A method of making tortillaflour as defined in claim 3, further comprising the steps of cookingdried grains of corn in the presence of lime and water, rinsing the thuscooked grains whereby the thus rinsed grains constitute said moistvegetables which are thereupon subjected to said compressing, kneadingand first homogenizing action.
 5. A method as defined in claim 1,further comprising the step of sealing said moist vegetables, said mass,said batches and said crumbs from the surrounding atmosphere.
 6. Amethod as defined in claim 1, wherein said steps of kneading,comminuting while homogenizing, and dividing immediately follow eachother and are carried out in a common housing in which the material is,up to the dividing step, continuously maintained under pressure.
 7. Amethod as defined in claim 2, wherein said subdividing step comprisesthe step of conveying the mass under pressure through a first set ofapertures and at least a second set of apertures having a smaller sizethan said first set whereby the mass is divided into a plurality of saidstrands during passing through each set of apertures, said homogenizingstep being carried out during the severing of said strands and duringconveying the material from said first to said second set of apertures.8. A method as defined in claim 1, wherein said compressing step iseffected by a rotary feed screw and the pressure supplied by such feedscrew is sufficient to maintain said moist vegetables, said mass andsaid batches in motion in the course of all of said steps.
 9. A methodas defined in claim 1, wherein the moisture content of vegetables priorto said first mentioned step is between 20 and 60 percent.
 10. A methodas defined in claim 9, wherein said moisture content is between 35 and55 percent.
 11. A method as defined in claim 1, further comprising thestep of cooking said vegetables in the presence of water prior to saidkneading step, and wherein said kneading, comminuting, homogenizing anddividing steps are carried out while the vegetables and portions thereofare still hot and contain at least some of said water.
 12. A method asdefined in claim 1, wherein said comminuting step comprises repeatedlysubdividing said mass into batches and said severing of said batchesbeing performed prior and/or subsequent to each subdivision thereof. 13.A method as defined in claim 12, further comprising the step ofhomogenizing the material subsequent to each of said severing steps. 14.A method as defined in claim 1, wherein said comminuting step comprisescutting the vegetables into fragments having maximum dimensions in therange of 1-2 millimeters.
 15. A method as defined in claim 1, whereinsaid first mentioned step comprises conveying moist vegetables in atleast one helical path between the external threads of a rotary feedscrew and the internal surface of a cylindrical barrel for the feedscrew.
 16. A method as defined in claim 15, wherein the width of saidpath is between 3 and 13 millimeters and said path takes up up to 30percent of the interior of said barrel.
 17. A method as defined in claim1, wherein said dividing step comprises passing said material throughthe holes of an extruder to form individual strands and subdividing saidstrands into said crumbs.
 18. A method as defined in claim 1, furthercomprising the steps of drying and thereupon grinding said crumbs.
 19. Amethod as defined in claim 18, wherein said drying step comprisesseveral successive stages.
 20. A method as defined in claim 19, whereinone of said stages includes agitating said crumbs.
 21. A method asdefined in claim 1, further comprising the step of reducing the speed ofmaterial immediately preceding said dividing step.
 22. A method asdefined in claim 1, wherein said subdividing step comprises conveyingsaid mass through at least one set of apertures and said dividing stepcomprises conveying homogenized material through a set of holes, thespeed at which said mass is conveyed through said apertures being atleast four times the speed at which the material passes through saidholes.